In currently available tire uniformity inspection machines, testing is fully automated. Tires are fed by conveyor to a test station where each tire is mounted upon two rim halves, inflated to a predetermined pressure and rotatably driven at a standard speed with its tread surface in abutting contact with the circumferential surface of a loadwheel. To mount a tire upon rim halves, a vertically movable upper rim is supported in the top of the machine and is mounted for movement towards and away from a lower rim mounted to a fixed, motor driven spindle mounted to the base of the machine. Other machines use a vertically movable lower rim that is supported in the base of the machine and is mounted for movement towards and away from an upper rim mounted to a fixed, motor driven spindle mounted to the top of the machine. In either case the tire is engaged between the rim halves and then testing.
To ensure proper alignment of the rim halves, the rim halves are mounted to machine members that include a male and female conical taper. Typically the upper rim half is mounted to an upper chuck assembly which includes the female conical taper and the lower rim half is mounted to the spindle assembly which includes the male conical taper. The engagement between the female conical taper and the male conical taper maintains precise alignment of the upper chuck assembly and rim half with the spindle assembly and other rim half. The movable rim half is commonly actuated by a hydraulic cylinder capable of moving the rim half quickly to engage the tire and capable of holding the rim half in place against the force created by the air pressure within the tire.
During operation of the machine, occasions occur where the tire is not placed in the proper location for engagement by the rim halves. The axis of rotation of the tire is not sufficiently close to the axis of rotation of the rim halves to ensure proper engagement. This mislocation can result in the tire being pinched by the rim halves or pinched between the male and female conical tapers, permanently damaging the tire. This is commonly called a mis-chuck. Additionally, since the tire is not concentric with the rim halves, one part of the circumference of the tire extends further away from the rim halves in a radial direction than would be if the tire was properly engaged. If the spindle is rotated in this condition, the part of the tire extending further from the rim halves can impact with various precision measurement devices placed in close proximity of the tire resulting in possible damage to the devices and/or tire.
Damaged tires must be destroyed. This is a significant cost to the manufacturer since almost all of the manufacturing costs have already been incurred at the time of damage. Costs are also incurred by machine damage or by additional effort spent to protect the machine from damage. When this occurs there is also a cost of lost production due to stopping the machine to clear the mis-chucked tire and possibly repair machine damage.
Some tire uniformity inspection machines monitor the hydraulic pressure required to close the rim halves. If the pressure is too great at a position of the movable rim half where a great pressure normally is not seen, then the operation is stopped before damage is done to the tire or machine. U.S. Pat. No. 5,390,540 to Mallison illustrates an example of this type of apparatus. However, some contact force is required to generate the pressure increase. This contact may leave a mark on the tire which may not be acceptable by the tire manufacturer.